This invention relates to a plain bearing, and more particularly to a plain bearing for use with a shaft which bearing has a specified portion in a circumferential direction to which a shaft load is applied in a concentrated manner.
There is well known a plain bearing in which an overlay, composed of Pb, Sn, Al, or an alloy comprising one of these substances as a main component, is formed on a surface of a bearing alloy layer so as to enhance the conformability and foreign matter embeddability, thereby imparting an excellent anti-seizure property to the plain bearing. There has been proposed a technique in which hard particles are included in this overlay so as to enhance its wear resistance, and such a technique is disclosed, for example, in JP-A-3-219098 and JP-A-4-331817 filed by the Applicant of the present application.
JP-A-3-219098 discloses a plain bearing in which 0.3 to 25 vol. % of inorganic hard particles, having a particle diameter of not more than 15 .mu.m, are added to an overlay of Pb base alloy, thereby imparting excellent wear resistance to the plain bearing.
JP-A-4-331817 discloses a plain bearing in which inorganic hard particles have a mean particle diameter of not more than 1.5 .mu.m, and an overlay has surface roughness of not more than Rz 4 .mu.m, and by doing so, an anti-seizure property and fatigue resistance are enhanced without adversely affecting wear resistance.
One of a major cause of a breakdown of a plain bearing, used in an internal combustion engine, is the inclusion or intrusion of solid foreign matters such as dirt and wear debris into lubricating oil, in which case abnormal wear develops in the plain bearing, thereby causing seizure.
Recently, there has been a demand for a plain bearing of the type which can exhibit excellent foreign matter embeddability even upon inclusion of solid foreign matters into lubricating oil. There is also known a plain bearing having an explosion load-receiving region to which a load is applied in a concentrated manner, and its representative example is a plain bearing used at a big end portion of a diesel engine.